Question

Salve! I want to exit my GUI application (vb.net 4) using a commandline parameter. I should send this from the commandline:

myapplication.exe quit

-and an already running instance of the application should exit.
Now, I have a mutex detection in place so that I can only have one instance of the application running at a time. It seems that if I send a commandline, it won’t work on an already running application; it will only work on one that is launching.

Answer 1

Easy Send Message to Running Instance of Application

Hello, everyone! After finding this nice post here, looking for a way that a single application would do one thing with the first instance, but the second instance would cause the first instance do something else.

The value of this is that you can (with your own, additional programming) use this to achieve the effect of sending commandline parameters to a running application. You would actually use a second instance of the app to send the commandline parameters as messages to the first instance. It works okay on my Windows XP, but I’m rather new to vb.net, so if you’ve any improvements, I’d like to know!

So I adapted anoriginalidea’s nice example and below is my result. This is the bare-bones of it all, so you just see here the essentials of the process.

It works like this:

1. First, stick this here module in your application.
2. Then launch app1
3. you will get a message saying, “InterCom Server Reporting for Duty!”
4. now launch app2 – you will get a message (it is actually from app1!), saying “My name is
   really Bob!” to let you know that the function fired off.
5. then app2 will exit (you told it to in sub main) and
   then app1 will exit becuase app2 told it to exit when InterComClient()
   was called.

first add this as your sub main
the mutex will check to see if your application is already running or not.

Public Sub Main()
    Dim createdNew As Boolean = True
    Using mutex As New Mutex(True, "TestForKalatorMutexProcess", createdNew)
        If createdNew Then
            InterComServer()
            'BE SURE TO CHANGE myApplication TO YOUR PRIMARY FORM!
            Application.Run(new myApplication)
        Else
            InterComClient()
            application.exit()
        End If
    End Using
End Sub

Now Add this in a module in your application

Imports System.Runtime.Remoting
Imports System.Runtime.Remoting.Channels
Imports System.Runtime.Remoting.Channels.ipc 'You have to add this as a reference!

Public Module intercom
#Region "-------------InterShared-------------------------------------"
Public Interface ICommunicationService
    Sub SaySomething(ByVal text As String)
End Interface
#End Region

#Region "-------------InterComClient-------------------------------------"
'This will run on the second instance
Public Sub InterComClient(ByRef intercommessage As String)
    Try
        Dim ipcCh As New IpcChannel("myClient")
        ChannelServices.RegisterChannel(ipcCh, False)
        Dim obj As ICommunicationService = DirectCast(Activator.GetObject(GetType(ICommunicationService), "ipc://IPChannelName/SreeniRemoteObj"), ICommunicationService)
        obj.SaySomething(intercommessage)
        Thread.Sleep(1000)
        ChannelServices.UnregisterChannel(ipcCh)
    Catch ex As Exception
        'If you use this as a way to exit your application, be sure to discard this exception
        'because the InterCom Server won't be running to receive the closing of the channel
        'and it will throw a "Pipe Ended" error that can't be solved.
        'To "discard" the error, simply catch it and don't do anything.
        'Dim errmsg As New Messenger("Exception in InterComClient" & vbCr & ex.Message)
    End Try
End Sub
#End Region

#Region "-------------InterComServer-------------------------------------"
Public Class CommunicationService
    Inherits MarshalByRefObject
    Implements ICommunicationService
    Public Sub SaySomething(ByVal whatmessage As String) Implements ICommunicationService.SaySomething
        msgbox("InterCom Client Heard this : " & whatmessage)
        Application.exit
    End Sub
End Class

Public Sub InterComServer()
    Dim ipcCh As IpcChannel
    ipcCh = New IpcChannel("IPChannelName")
    ChannelServices.RegisterChannel(ipcCh, False)
    RemotingConfiguration.RegisterWellKnownServiceType(GetType(CommunicationService), "SreeniRemoteObj", WellKnownObjectMode.Singleton)
    MsgBox("InterCom Server Reporting for Duty!")
End Sub
#End Region

End Module

[update]

Just FYI for anyone, I’ve used this in my application now for awhile, and it seems to work very well.